The subject matter described herein generally relates to a radiation generator and more particularly to a high voltage tank assembly used in a radiation generator.
An imaging device comprising a ‘C’ arm incorporates a radiation generator and a radiation detector. The radiation generator generally comprises a radiation source, a high voltage tank assembly configured to energize the radiation source and a power circuit. As the high voltage tank assembly responsible for generating the high voltage required for the operation of the radiation source represents a substantial part of the overall size of the radiation generator, it is desirable to provide a compact high voltage tank assembly.
Further, the high voltage tank assembly comprises a voltage rectifier circuit and a transformer assembly coupled to the voltage rectifier circuit. The voltage rectifier circuit and the transformer assembly are among bulky modules of the radiation generator.
The transformer assembly is configured to include a high voltage transformer and/or a filament transformer. The conventional filament transformer comprises a primary winding, a first bobbin to house the primary winding, a secondary winding, a second bobbin to house the secondary winding, a core and a shield. The first bobbin, the second bobbin and the shield are placed concentrically with the primary winding close to the core. The secondary winding of the filament transformer is biased at the cathode potential of the X ray tube. Thus, the filament transformer may include one or more insulation sheets to strengthen the insulation between the secondary winding and the core thereby resulting in bulkiness of the filament transformer.
The voltage rectifier circuit comprises many electrical components such as diodes, capacitors and resistors for high voltage generation. From component manufacturing trend perspective and thereby as well from cost perspective, it is common to find use of SMD components in design. The diodes for the voltage rectifier circuit, for manufacturing and cost advantage, are increasingly desired in SMD packages. A plurality of SMD diodes with a PIV rating of about 1 kV are typically put in series to function as a high voltage diode. One limitation associated with use of the diode series is with regard to the dimension of the printed circuit board required to host the diode series.
Further, the choice of the capacitors for high voltage generation is based on the power requirement of the high voltage tank assembly. For mobile RAD application, the radiation generator is desired to be cost effective with a peak power requirement of about few kilo Watts. Capacitors with ceramic insulation are generally not suited for such an application as the peak power requirement is high and the duration is long. The ceramic capacitors carry a risk of loss of performance (high ripple) due to losses in ceramic. Alternatives such as high voltage capacitors with mica or polypropylene insulation generally result in bulky design for the radiation generator.
On the other hand, the art of using capacitors formed in the printed circuit board is a well-known technique. A dielectric material in between two conductive planes forms a capacitor, and in the printed circuit board existence of capacitance between two tracks or planes is a common knowledge. Prior art methods generally use the built-in capacitors as decoupling capacitors to swamp out parasitic effect, typically in an electronic industry in need of high packing density of electronic components. Thus, most of the activity with regard to the built in capacitance in the printed circuit board is concentrated around treatment of such capacitance for the purpose of decoupling, thereby inefficiently using the in built capacitance in the printed circuit board.
Hence, there exists a need to provide a compact and efficient design for assembling various components of the high voltage tank assembly used in the radiation generator.